Carbon blacks are generally produced in Furnace process. In this process, at first, a hydrocarbon fuel is burned with an excess amount of oxygen typically supplied as a flow of air or oxygen containing gas in the space having a lining of fire resistant material to produce a hot combustion gas. Then, a high molecular weight hydrocarbon oil as feedstock is injected in a plurality of streams to the hot combustion gas, and the feedstock is thermally decomposed and dehydrogenated to prepare an aerosol which contains carbon black particles suspended in the gas. Finally, the carbon black particles are separated from the gas and collected. The resultant carbon black collected as a fluffy powder can be pelletized by means of conventional pelletizing methods.
Since the carbon blacks of various characteristics and grades can be produced by adjusting various operating condition, for example, an amount and a position of the introduction of a fuel; an amount, a position and a manner of a introduction of feedstock and oxygen containing gas; a position of quenching; a diameter of reactor and so on, most of carbon black is produced in this process at the present.
Carbon blacks are produced in large quantities throughout the world and commonly used as reinforcing filler for an elastomer and as pigment or colorant for a plastic, a paint and a printing ink. The largest application field of a carbon black is a manufacture of pneumatic tires for automotive and aircraft, wherein the carbon black is used as reinforcing filler for a rubber matrix to impart mechanical strength and wear resistance to it.
Recently, the problems from environmental and/or safety aspects are emphasized in the tire industry, and a further demand for lower fuel consumption, longer service life and improved grip performance are intensified. Although a rubber itself must be improved, a carbon black is also requested to improve for such demands. That is, a carbon black is required to control not only conventional macroscopic properties, such as a specific surface area and a structure, but also microscope properties, such as a particle size, an aggregate size and distributions of them. Therefore, it becomes important to develop the carbon black reactor which can easily control these microscopic properties. In addition, there is need for carbon black reactor which can increase the output of the carbon black, and which can effectively utilize the thermal energy of the hot combustion gas.
In order to solve the above-mentioned problems, many techniques and patents relating to the geometry and the operating condition of a carbon black reactor have bean disclosed.
As mentioned above, since a carbon black is produced by injecting the feedstock into the hot combustion gas occurred from burning the hydrocarbon fuel with the oxygen containing gas, and thermally decomposing and/or incompletely combusting the feedstock, the manner of contact of the hot combustion gas and the feedstock has much influence upon the physical or chemical characteristics of the carbon black, especially the properties of the aggregate, unit particle size which said aggregate is composed, and the distribution of said size. Therefore, there is prior art that the contact condition is altered to improve the characteristics of the carbon black. For example, it is disclosed that the contact condition is changed by introducing the carbon black separately produced in different contact condition to the feedstock introducing chamber to widen the distribution of the aggregate size (For example, Japanese patent publication No. Hei64-4659, Applicant: Tokai Carbon Co., Ltd).
In other prior art, to achieve the high efficiency for the use of heat energy, the facility for scale up, the high output of product, and the ability to produce high quality product, the feedstock is introduced into the hot combustion gas in the form of a plurality of individual coherent streams substantially from the exterior periphery and a plurality of individual coherent streams outwardly, substantially transversely from at least one location in the interior (U.S. Pat. No. 3,922,335, Assignee: Cabot Corporation).
In another example, the reaction chamber of the carbon black reactor was defined by a plurality of flat planes so that the cross-section shape of the flow of the hot combustion gas substantially conforms to the spray pattern of the feedstock, thereby providing a minimum flame length within the reactor and more efficient use of the hot combustion gas (U.S. Pat. No. 5,256,388, Assignee: Colombian Chemicals Company).
In the meantime, considering the temperature and the flow velocity of the hot combustion gas at the position where the feedstock is introduced (the flow velocity may be extremely high such as approximate sound velocity), when the feedstock is introduced to the hot combustion gas, especially in the atomized form, the feedstock would be flowed by the flow of the hot combustion gas toward a downstream. In case that the space where feedstock is introduced is narrow, however, contact efficiency of the hot combustion gas and the feedstock is high because most of the cross-section of the feedstock introduction part is covered with the feedstock (FIG. 8).
On the other hand, when a cross-section of the feedstock introduction part is widened in order to increase a amount of the feedstock introduced, which in turn leads to increase a output of a carbon black, the hot combustion gas which does not contact with the feedstock and passes toward the downstream is increased especially at the central region of said part (FIG. 9).
As compared with FIG. 8 and FIG. 9, it is clearly understood that the contact efficiency between the hot combustion gas and the feedstock in the carbon black reactor having enlarged feedstock introduction part is considerably lower than that in the reactor having narrow feedstock introduction part.
This is a reason why there is the difference in the carbon black characteristics, such as the distributions of unit particle size and the aggregate size between the pilot-scale reactor, which has a narrow feedstock introduction part, and the reactor actually operated. That is, in the pilot-scale reactor, the both distributions are narrow, whereas in the reactor actually operated, said distributions are wider than the former.
As mentioned above, when a carbon black is produced in the reactor actually operated, it is very difficult to obtain the product having the characteristics of one produced in the pilot-scale plant. Accordingly, if narrow distribution of the unit constituent particle size and the aggregate size is required for the carbon black, use of many pilot-scale reactors at the same is an only measure to produce it having such characteristics in the large scale.